Method of biaxially deforming sheet material

ABSTRACT

Sheet material is deformed, for example crimped or bulked by feeding it to the surface of a rotating roll having a multiplicity of depressions in its surface and pressing the material against the roll surface, the material being fed to the roll at a rate exceeding the linear peripheral speed of the roll. Examples of materials which may be so deformed are filaments consisting of or containing thermoplastic polymers, woven and non-woven fabrics, thermoplastic sheets, paper and metal foils. Preferably, the roll surface consists of sintered particulate material, the depressions being the voids between adjacent particles.

United States Patent 91 van Tilburg [54] METHOD OF BIAXIALLY DEFORMINGSHEET MATERIAL [75] Inventor: Jan van Tilburg, Alkmaar, Nether- I lands[73] Assignees American Can Company, Greenvwich,Conn.

[22] Filed: Feb. 3, 1970 21 Appl. No.2 8,342

[30] Foreign Application Priority Data 1 Feb. 6, 1973 2,294,957 9/1942Caldwell ..28/72.15 X 2,435,891 2/1948 Lodge ....28/72.15 X 2,627,6442/1953 Foster..... ....28/72.15 X 2,668,430 2/1954 Laros ....28/72.15 X3,336,645 8/1967 Mirsky ..28/1.8 3,399,101 8/1968 Magid ..156/219 X3,444,035 5/1969 Bushnell i ..156/219 X 3,446,685 5/1969 Goldstone eta1. ..l56/219 3,514,362 5/1970 Chavannes ..l56/219 X PrimaryExaminerLouis K. Rimrodt AttorneyRobert P. Auber [57] ABSTRACT Sheetmaterial is deformed, for example crimped or bulked by feeding it to thesurface of a rotating roll having a multiplicity of depressions in itssurface and pressing the material against the roll surface, the materialbeing fed to the roll at a rate exceeding the linear peripheral speed ofthe roll. Examples of materials which may be so deformed are filamentsconsisting of or containing thermoplastic polymers, woven and non-wovenfabrics, thermoplastic sheets, paper and metal foils. Preferably, theroll surface consists of sintered particulate material, the depressionsbeing the voids between adjacent particles.

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A TORNEYS Hall INVENTOR B tIJIV Ww mama I ATTORNEYS METHOD OF BIAXIALLYDEFORMING SHEET MATERIAL This invention is concerned with a method ofdeforming filamentary and sheet material.

According to the invention, there is provided a method of deformingfilamentary and sheet material (as herein defined) which comprisesfeeding the material to a rotating roll at a rate exceeding the linearperipheral speed of the roll, and pressing the material into contactwith the curved surface of the roll, which surface is provided with amultiplicity of depressions.

By filamentary and sheet material is meant thermoplastic filaments,yarns consisting of or comprising thermoplastic filaments or fibers,knitted fabrics, woven and non-woven fabrics, thermoplastic tapes andfilms and paper and metal foils.

In the method of the invention, the material is deformed by beingpressed into the depressions on the roll surface and the precise natureof the deformation depends, inter alia, on the-size and distribution ofthe depressions, the pressure applied to the material and the feed rateof material to the roll.

The size and distribution of the depressions on the roll surface mayvary widely. For example, the depressions may be very small incross-sectional area so that there are hundreds or thousands per squareinch of roll surface. Alternatively, they may be relatively large andtake the form of, for example, grooves extending across the surface ofthe roll. Depressions of a size intermediate these two examples may beused and the depressions need not all be the same size. The depressionsmay be regularly or irregularly spaced on the roll surface.

The shape of the depressions can vary widely and the depressions may beshallow or deep. In the latter case when the roll is a cylinder, thedepressions may take the form of holes in the cylinder wall. Thepresence of sharp edges on the roll surface should, of course, beavoided since these may tend to tear the material being deformed.

The depressions may be formed on a roll surface in any suitable mannersuch as by etching or machining. However, when it is desired that theroll surface should contain a very large number of small cross-sectionalarea depressions, a roll having a surface formed of sintered particulatematerial is particularly satisfactory. The surface portion of such aroll consists of a very large number of particles sintered together withvoids or cavities between adjacent particles, which cavities form thesurface depressions.

Rolls having such sintered surfaces can be prepared by known techniquesand the size of the depressions or cavities controlled by varying thesize of the particles. For example, surfaces can be produced with fromless than 10,000 to more than 200,000 cavities per square inch. Suitableparticulate materials for these surfaces include metals and alloys suchas bronze and polymeric materials such as polytetrafluoroethylene.

When sheet material is treated by the process of the invention, it maybe deformed either monoaxially or biaxially depending on the nature andarrangement of the depressions on the roll surface. For example, when agrooved roll is used with the grooves extending parallel to the rollaxis, and the roll axis is perpendicular to the direction of movement ofthe material, only the length (and not the width) of the material isreduced by the deformation process. The material has been monoaxiallydeformed and the stretchability of the material is then only increasedalong one axis (its length). When, however, the multiplicity ofdepressions are arranged so that both the width and length of the sheetmaterial are reduced in the deformation step, the stretchability isincreased along two axes and the material is said to be biaxiallydeformed. A sintered roll surface results in biaxial deformation.

The method of the invention is particularly useful for imparting monoorbi-axial stretchability to materials.

The pressure applied to the material whilst it is in contact with theroll also affects the type and degree of deformation obtained. Thematerial may be pressed against the roll surface and into thedepressions in any suitable manner such as, for example, by gaspressure. Gas pressure may be applied by increasing the gas pressure onthe outside of the material and/or, in the case of a cylindrical roll inwhich the depressions or cavities extend through the cylinder wall, byreducing the gas pressure within the roll.

Alternatively, or in addition, the material may be pressed against theroll surface and into the depressions by means of an auxiliary rotatingroll or moving belt. The auxiliary roll (or belt) is rotated at a speedhigher than the linear peripheral speed of the main roll so as to forceor stuff the material into the depressions. The auxiliary roll may havea smooth continuous surface which may, for example, be of metal or aresilient material such as rubber, or it may have depressions, forexample it may be formed of sintered particles similar to the main roll.

The feed rate of material to the roll must be greater than the linearperipheral speed of the roll and high enough to provide sufficientmaterial at the roll surface for the desired deformation.

According to a modification of the process of the invention, thematerial is deformed in two or more steps, i.e., by contacting it two ormore times with the same roll or with two or more different rolls.

Examples of materials which may be deformed by the method of thisinvention include thermoplastic filaments and yarns such as nylon,polypropylene, glass and metal; woven (or knitted) and non-wovenfabrics; thermoplastic tapes and films such as polyethylene orpolypropylene film; paper; and metal foils such as aluminum foil. Whenpaper is deformed by the method of the invention, the paper ispreferably treated whilst it is slightly damp.

With certain materials such as those containing thermoplastic polymers,it may be desirable to set the deformation. This may be effected byheating the material prior to, or during, the deformation andsubsequently allowing the material to cool in the deformed condition.The material may be heated during the deformation by, for example, usinghot gas to press the material against the roll surface or by using aheated roll.

The deformation may be set" in metal foils by, for example, coating thedeformed foil with a stretchable adhesive or film so that when thecoated deformed foil is stretched and released, it will return to itsoriginal deformed configuration.

The material treated by the method of the invention may be a laminate.Alternatively, lamination may be effected simultaneously with thedeformation by, for example, feeding to the roll surface two layers ofmaterial, one superimposed on the other so that the layers becomelaminated by mechanical interlocking as a result of the deformation.

Various types of deformation can be formed by the process of theinvention. For example, the material may be crimped either monoaxiallyor biaxially. The degree of crimping can be varied by varying the rateof feed of material, the pressure and the size and distribution of thedepressions. The size or depth of the crimp also depends on thesefactors, particularly on the depth of the depressions in the rollsurface.

When fibrous sheet material is treated in the process of the invention,it is possible to effect bulking, that is to decrease (not increase) thebulk density of the material. By selecting the appropriate depressiondimensions on the roll surface (the depth and the length in the machinedirection are particularly important), the feed rate and the pressure,it is possible to produce biaxially stretchable very light-weightnonwoven fabric materials and biaxially stretchable lightweight foamed"paper which has heat insulating properties. Mono-axially stretchablebulked fibrous materials may also be made in a similar manner.

In the case of non-woven fiber sheets, it is possible by the process ofthe invention to effect a re-arrangement of the fibers. For example, anon-woven, unbonded, slightly bonded or fully bonded sheet of fibers inwhich the fibers are arranged in the machine direction may be deformedusing a sintered roll surface, to form an open weave" product. Theproduct may then itself be bonded or treated to set the deformation.

When thermoplastic films are treated by the method of the invention, adeformed material which is fabric or foam-like may be formed. When alengthwise highly oriented film is used, deformation may also result inlengthwise splitting of the film and, through intertwining, in theformation of a fabric-like structure.

It is to be understood that the type of deformation produced by themethod of this invention and the resulting effect thereof on thematerial, may vary widely. Routine variation in the process parameterscan produce widely differing effects but selection of the desireddeformation and the optimum conditions appropriate therefor can readilybe made by trial and experiment by one skilled in the art.

In the case of thermoplastic materials, the material is preferablyheated before contact with the roll to facilitate deformation of thematerial.

In order that the invention may be more fully understood, reference ismade to the accompanying drawings, in which FIG. 1 is an enlargedsection of part of the sintered surface of a roll also showing thematerial being deformed;

FIG. 2-5 and 8 are cross sections through deformed material showing theconfiguration of the deformation;

FIG. 6 is a schematic sectional view of material being deformedcontinuously on a roll;

FIG. 7 is a schematic sectional view similar to FIG. 6, with thematerial pressed against the main roll by means of an auxiliary roll;

FIG. 9 is similar to FIG. 7 but illustrates the use of a belt in placeof the auxiliary roll;

FIG. 10 shows in plan view a thermoplastic film which has been deformedby the method of the invention;

FIG. 11 is a schematic sectional view of paper which has been bulked bythe method of the invention;

FIG. 12 illustrates the bulking of fibrous sheet material;

FIG. 13 illustrates the rearrangement of fibers effected by the methodof the invention; and

FIG. 14 illustrates, in plan view, various possible shapes for thedepressions on the roll surface.

Referring to FIG. 1 of the drawings, part of the roll surface is shownas comprising a number (five) of particles l which touch, and aresintered to, other similar particles (not shown). Depressions orcavities 2 are formed between the particles and the material to bedeformed 3 (shown as, for simplicity, a thermoplastic filament) ispressed into these depressions to an extent depending on the pressureand the rate of feed of material. The varying degrees and type ofdeformation obtainable are illustrated by the discontinuous lines 4, 5and 6 which show the possible positions of the material for differentdegrees of deformation. The deformed material obtained is illustrated inFIGS. 2 to 5, FIG. 2 showing the deformation obtained when the materialis in the main position shown in FIG. 1 and FIGS. 3 to 5 showing thecrimp when the material is in positions 4, S and 6 (respectively) inFIG. 1.

In the arrangement shown in FIG. 1, the material is suitably pressedagainst the sintered particle roll surface by gas pressure by increasingthe pressure at B and/or reducing the pressure at S.

In FIG. 6 of the drawings, the rotating roll 10 has a multiplicity ofdepressions on its surface and the material 3 is pressed against thesurface by gas pressure at B. A guide surface 11 is provided for thematerial to be deformed.

FIG. 7 illustrates the use of an auxiliary roll 12 to press the materialagainst the surface of roll 10. The direction of rotation of the rollsl0 and 12 and the direction of movement of the material 3 are shown byarrows. 1

FIG. 9 illustrates the use of a belt 13 in place of the auxiliary roll12. One advantage of using such a belt is that it exerts a pressure onthe material 3 over a much greater area of the roll 10 than does asingle auxiliary roll.

The shape of the deformation of a filament can be relatively simple, asshown for example in FIGS. 2 and 3, or it can be relatively complex asshown in FIGS. 5 and 8.

FIG. 10 illustrates the biaxial deformation of a thermoplastic film (inwhich the deformation has been set). The deformed film is fabric-likeand highly stretchable. The solid lines indicate the dimensions of thedeformed film and the dashed lines the original dimensions of the sheetbefore deformation. The roll surface used had depressions causingdeformation at points X and the lines Y indicate creases or foldsarising from deformation at the points X. The machine direction (M) isindicated by the arrow.

FIG. 11 illustrates (in cross-section) paper which has become bulked orblown up by the method of the invention. In this case, the paper hasbeen passed over a roller formed with grooves extending parallel to theaxis of the roller and perpendicular to the machine direction. The paperis thus mono-axially deformed.

The principle of bulking of fibrous sheets is illustrated in FIG. 12which shows a bundle of fibers which, when treated by the method of theinvention, assume the shape 15A or 158 depending on whether the bundleis relatively long or short, respectively. In the first case 15A, allthe fibers are deformed in the same direction, but in the second casethe fibers go in different directions causing a bulking effect 15B.

FIG. 13 illustrates the rearrangement of fibers which can be effected bythe method of the present invention. A non-woven sheet of fibers 16 inwhich the fibers are predominantly arranged in the machine direction Mis treated by the method of the invention using a sintered surfaceroller. An open-weave type product is obtained 17.

FIG. 14 illustrates various shapes (in plan view) of the depressionswhich may be used on the surface of the roll.

The deformed material may be subjected to an aftertreatment such as coldor hot rolling. The material, before being deformed, may be subjected toa pre-treatment, for example thermoplastic films may be perforatedbefore deformation.

What I claim is:

l. A method of imparting biaxial stretchability to sheet materialwhichcomprises feeding the material to a rotating roll provided with amultiplicity of depressions at a rate exceeding the linear peripheralspeed of the roll, and pressing the material into contact with thecurved surface of the roll and into the depressions to deform the sheetmaterial so that both the length and width of the material are reducedby the deformation step.

2. A method according to claim 1 wherein the material is pressed againstthe surface of the roll by gas pressure.

3. A method according to claim 1 wherein the curved surface of the rollis formed of sintered particulate matter.

4. A method according to claim 3 wherein the particulate matter isbronze.

5. A method according to claim 1 wherein the depressions have beenformed in the surface of the roll by etching.

6. A method according vto claim 5 wherein the material is pressedagainst the surface of the roll by an auxiliary rotating roll.

7. A method according to claim 6 wherein the linear peripheral speed ofthe auxiliary roll is greater than the linear peripheral speed of thesaid roll.

8. A method according to claim 7 wherein the said auxiliary roll has aresilient rubber curved surface.

9. A method according to claim 7 wherein said auxiliary roll also has asurface provided with a multiplicity of depressions.

10. A method of biaxially deforming sheet material which comprisesheating the material, at a temperature sufficiently high to allowdeformation thereof, to a rotating roll provided with a multiplicity ofdepressions at a rate exceeding the linear peripheral speed of the roll,and pressing the material into contact with the curved surface of theroll and into the depressions whereby the material is crimped andbulked.

11. method accordlng to claim 10 wherein the material is pressed againstthe surface of the roll by the pressure of hot gas which serves also toheat the material.

12. A method according to claim 10 wherein the curved surface of theroll is formed of sintered particulate matter.

13. A method according to claim 12 wherein the particulate matter ispolytetrafluoroethylene.

14. A method according to claim 10 wherein the depressions have beenformed in the surface of the roll by machining.

15. A method according to claim 14 wherein the I material'is pressedagainst the surface of the roll by an auxiliary rotating roll.

16. A method according to claim 15 wherein the linear peripheral speedof the auxiliary roll is greater than the linear peripheral speed of thesaid roll.

1. A method of imparting biaxial stretchability to sheet material whichcomprises feeding the material to a rotating roll provided with amultiplicity of depressions at a rate exceeding the linear peripheralspeed of the roll, and pressing the material into contact with thecurved surface of the roll and into the depressions to deform the sheetmaterial so that both the length and width of the material are reducedby the deformation step.
 2. A method according to claim 1 wherein thematerial is pressed against the surface of the roll by gas pressure. 3.A method according to claim 1 wherein the curved surface of the roll isformed of sintered particulate matter.
 4. A method according to claim 3wherein the particulate matter is bronze.
 5. A method according to claim1 wherein the depressions have been formed in the surface of the roll byetching.
 6. A method according to claim 5 wherein the material ispressed against the surface of the roll by an auxiliary rotating roll.7. A method according to claim 6 wherein the linear peripheral speed ofthe auxiliary roll is greater than the linear peripheral speed of thesaid roll.
 8. A method according to claim 7 wherein the said auxiliaryroll has a resilient rubber curved surface.
 9. A method according toclaim 7 wherein said auxiliary roll also has a surface provided with amultiplicity of depressions.
 10. A method of biaxially deforming sheetmaterial which comprises heating the material, at a temperaturesufficiently high to allow deformation thereof, to a rotating rollprovided with a multiplicity of depressions at a rate exceeding thelinear peripheral speed of the roll, and pressing the material intocontact with the curved surface of the roll and into the depressionswhereby the material is crimped and bulked.
 11. A method according toclaim 10 wherein the material is pressed against the surface of the rollby the pressure of hot gas which serves also to heat the material.
 12. Amethod according to claim 10 wherein the curved surface of the roll isformed of sintered particulate matter.
 13. A method according to claim12 wherein the particulate matter is polytetrafluoroethylene.
 14. Amethod according to claim 10 wherein the depressions have been formed inthe surface of the roll by machining.
 15. A method according to claim 14wherein the material is pressed against the surface of the roll by anauxiliary rotating roll.